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#include "tommath_private.h"
#ifdef BN_MP_DIV_2_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* b = a/2 */
mp_err mp_div_2(const mp_int *a, mp_int *b)
{
int x, oldused;
mp_digit r, rr, *tmpa, *tmpb;
mp_err err;
/* copy */
if (b->alloc < a->used) {
if ((err = mp_grow(b, a->used)) != MP_OKAY) {
return err;
}
}
oldused = b->used;
b->used = a->used;
/* source alias */
tmpa = a->dp + b->used - 1;
/* dest alias */
tmpb = b->dp + b->used - 1;
/* carry */
r = 0;
for (x = b->used - 1; x >= 0; x--) {
/* get the carry for the next iteration */
rr = *tmpa & 1u;
/* shift the current digit, add in carry and store */
*tmpb-- = (*tmpa-- >> 1) | (r << (MP_DIGIT_BIT - 1));
/* forward carry to next iteration */
r = rr;
}
/* zero excess digits */
MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used);
b->sign = a->sign;
mp_clamp(b);
return MP_OKAY;
}
#endif
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